With the advent of high strength plastics having a low co-efficient to friction, plastic plates have been developed which cover the fifth wheel and act as a bearing surface between the trailer and the tractor. Such attachments have been disclosed in prior U.S. Pat. Nos. 3,337,277, 3,704,924, 3,924,909, 4,121,853, 4,542,912 and 4,169,635.
The prior art attachments described in these patents have proved to be beneficial in reducing the maintenance of the fifth wheel by reducing the need for greasing the fifth wheel. However, the prior art devices are generally bolted, riveted onto the fifth wheel using countersunk screws. Such attachments have improved the life of the fifth wheel. However, the method of attachment has proved to be unsatisfactory as the plate becomes damaged after prolonged use due to increased movement between the plate and the fifth wheel as a result of the screws becoming worn and the heads of the screws being sheared.
Still other attachments have used a rivet having an axial bore. The rivet is placed in a counter-sunk bore in the face of the plastic plate and then welded to the fifth wheel. Such method of attachment has also proved unsatisfactory as the rivets become dislodged after prolonged use.